[Note: This UCSD GCRC protocol utilized the UVA GCRC VAX computer for (continued) access to CLINFO software for data analysis.] This study examines the effect of salt and stress on blood pressure regulation with particular emphasis on the sympathetic nervous system and the renin angiotensin system. Patients are studied on a low-salt diet (10 mEq. sodium/day) during 2 hospitalizations where they receive, in a double-blind fashion, either placebo or an angiotensin-converting enzyme inhibitor. COMPUTER ONLY.